A display screen may comprise a large number of display dots. Each dot is driven by a small electric current or voltage. It changes or retains its color in response to the voltage or current impressed on it.
In a multicolor electrochromic display (including black/white and monochrome/colorless), dots displaying different colors are generally at different voltages, and will discharge to a common voltage (and, thus, to a common color) unless they are isolated from one another, or unless a refreshing voltage or current is periodically impressed on them. Isolation by conventional circuitry generally slows response time, or diminishes resolution, or both. Refreshment increases power consumption.